Natural Resources
Conservation Service
Ecological site R044AA162MT
Thin Loamy (Tlo) LRU 44A-A
Last updated: 2/05/2022
Accessed: 11/21/2024
General information
Provisional. A provisional ecological site description has undergone quality control and quality assurance review. It contains a working state and transition model and enough information to identify the ecological site.
MLRA notes
Major Land Resource Area (MLRA): 044A–Northern Rocky Mountain Valleys
For further information regarding MLRAs, refer to:
http://soils.usda.gov/survey/geography/mlra/index.html
Land Resource Unit (LRU) 44A-A:
• Moisture Phase: xeric, dry - ustic, dry
• Temperature Phase: frigid warm
• Dominant Cover: rangeland
• Representative Value(RV) Effective Precipitation: 10-14 inches
• RV Frost-Free Days: 90-120 days
Site Concept:
Site does not receive any additional water.
Soils are:
• moderately deep, deep, or very deep with < 15% stone and boulder cover.
• not skeletal within 20” of soil surface.
• not strongly or violently effervescent in surface mineral 4”.
Slope is > 15%.
Soils do not have a mollic epipedon.
Surface textures usually range from very fine sandy loam to clay loam.
Clay content is < 32% in surface mineral 4”.
Associated sites
| R044AA161MT |
Thin Clayey (Tcy) LRU 44A-A |
|---|---|
| R044AA038MT |
Droughty Steep (Drstp) LRU 44A-A |
| R044AA136MT |
Shallow Loamy (Swlo) LRU 44A-A |
Similar sites
| R044AA161MT |
Thin Clayey (Tcy) LRU 44A-A This site occupies the same landscape positions and differs mainly by soil texture and plant community. |
|---|---|
| R044AA136MT |
Shallow Loamy (Swlo) LRU 44A-A This site differs by having shallower soils (10-20 |
| R044AA032MT |
Loamy (Lo) LRU 44A-A This site differs by being on slopes <15%. |
| R044AA038MT |
Droughty Steep (Drstp) LRU 44A-A This site differs by being loamy-skeletal at 10-20 |
Table 1. Dominant plant species
| Tree |
Not specified |
|---|---|
| Shrub |
Not specified |
| Herbaceous |
(1) Pseudoroegneria spicata |
Physiographic features
The Thin Loamy (TLo) ecological site (R044AA162MT) is located LRU “A” in MLRA “44A.” This ecological site occurs on moderately steep to steep alluvial fans, stream terraces, till plains, lake plains, or moraines. The slope is > 15%. This site occurs on all exposures; effect of aspect can be significant in LRU assignment.
Table 2. Representative physiographic features
| Landforms |
(1)
Lake plain
(2) Lake terrace (3) Stream terrace |
|---|---|
| Elevation | 1,800 – 5,000 ft |
| Slope | 15 – 50% |
| Water table depth | 42 in |
| Aspect | E, S, W |
Climatic features
The dissected Northern Rocky Mountain Valleys of MLRA 44A are considered to have a maritime climate. Precipitation is fairly evenly distributed throughout the year with less than about 35% of the annual precipitation occurring during the growing season in Montana. Rainfall occurs as high-intensity, convective thunderstorms in the spring and fall. Most of the precipitation in the winter is snow or rain on fully or partially frozen ground. Average precipitation for LRU-A is 12”, and the frost-free period averages 105 days.
See Climatic Data Sheet for more details (Section II of the Field Office Technical Guide: http://efotg.nrcs.usda.gov/efotg_locator.aspx?map=MT) or reference the following climatic Web site: http://www.wrcc.dri.edu/climsum.html.
Table 3. Representative climatic features
| Frost-free period (average) | 120 days |
|---|---|
| Freeze-free period (average) | 140 days |
| Precipitation total (average) | 14 in |
Figure 1. Monthly average minimum and maximum temperature
Influencing water features
Soil features
These soils are moderately deep to very deep and surface textures (< 2 mm) range from very fine sandy loam to clay loam. Structure is weak to nonexistent in the subsoil, which decreases the stability of the site.
Table 4. Representative soil features
| Surface texture |
(1) Silt loam (2) Loam (3) Clay loam |
|---|---|
| Family particle size |
(1) Loamy |
| Drainage class | Well drained |
| Permeability class | Moderately slow to moderately rapid |
| Soil depth | 20 in |
| Available water capacity (0-40in) |
3.5 – 7.5 in |
| Calcium carbonate equivalent (0-40in) |
20% |
| Electrical conductivity (0-40in) |
1 mmhos/cm |
| Sodium adsorption ratio (0-40in) |
12 |
| Soil reaction (1:1 water) (0-40in) |
6.3 – 8.2 |
Ecological dynamics
The Thin Loamy ecological site is characterized by the production and composition of plant species in the Reference Plant Community, which is defined by soils, precipitation, and temperature regime influencing the site. The presumed Reference Plant Community of this site is dominated by cool-season perennial bunchgrass species, primarily bluebunch wheatgrass (Pseudoroegneria spicata) with minor components of perennial forbs and Wyoming big sagebrush (Artemisia tridentata). LRU-A occurs in the valleys of western Montana, on rangelands with a xeric, dry or ustic, dry soil moisture phase, a frigid, warm soil temperature phase, 10-14” of effective precipitation, and between 90 and 120 consecutive frost-free days annually. This site is characterized by medium-textured surface horizons with soils more than 20” deep and slopes < 15%.
The majority of precipitation comes early in the form of snow and spring rain. Summers are usually dry. The growing season is short and cool; primary growth typically occurs between May and July, and dominant plants are those that have adapted to these conditions.
In response to disastrous fires in 1910, new firefighting policies were established. Wildland fire suppression became an important driving factor in the ecology of western rangelands. Livestock grazing during the late 1800s and early 1900s often occurred at very heavy levels. Heavy grazing resulted in a severe reduction in fine fuels, which further reduced potential for natural fires. These two actions altered the natural fire interval.
Fire suppression, along with fine-fuels reduction, has interfered with the natural fire interval; many areas have not burned for over 100 years (Arno and Gruell 1986). Prior to 1900, the average natural fire return intervals were probably shorter than 35 years for this MLRA. Historic fire frequency may have ranged from 15 to 75 years. Trees and non-sprouting shrubs were restricted to small patches or widely spaced plants. Following fire on medium-textured soils, perennial bunchgrasses apparently recovered in a few years and were present to fuel subsequent fires, which suppressed woody species and kept them as a minor component of the community (Arno and Gruell 1983).
Historical records indicate, prior to the introduction of livestock (cattle and sheep) during the late 1800s, elk and bison grazed this ecological site. Evidence shows periodic use by bison, in large numbers and concentrations. Forage for livestock was noted as minimal in areas recently grazed by bison (Lesica and Cooper 1997).
Significant livestock grazing has occurred on most of this ecological site in western Montana for more than 100 years (beginning with the 1860’s gold boom and subsequent settlement through 1900). Indian horse herds were present and numerous for several hundred years prior. The primary type of European livestock grazed in this region has historically transitioned between sheep and cattle with early grazing (pre-1890) dominated by the cattle industry. In the 1890s Montana sheep production began to increase dramatically (> 400%) and dominated the cattle industry for approximately four decades. By the 1930s livestock production once again favored the cattle industry, which continues to dominate livestock grazing in the region today (Wyckoff and Hansen 2001). The Thin Loamy ecological site is relatively accessible, and many examples were subject to heavy and/or season-long grazing until 1970 or later.
Invasive species are an important part of the ecology of MLRA 44A. Notable invasive species include spotted knapweed (Centaurea stoebe), leafy spurge (Euphorbia esula), sulphur cinquefoil (Potentilla recta), and cheatgrass (Bromus tectorum). Invasive species impact almost every site in MLRA 44A. Sites are either currently invaded or have been treated to kill invasives, which can reduce production and change composition of forbs and shrubs. Even where invasives are not present, the threat of invasion drives management of this site.
Although there is considerable qualitative experience supporting the pathways and transitions within the State and Transition Model (STM), no quantitative information exists that specifically identify threshold parameters between grassland types and invaded types in this ecological site. For information on STMs, see the following citations: Bestelmeyer el al. 2003, Stringham et al. 2003, Bestelmeyer et al. 2004, and Bestelmeyer and Brown 2005.
Rangeland Health Reference Worksheets have been posted for this site on the Montana NRCS Web site (www.mt.nrcs.usda.gov) in Section II of the eFOTG under (F) Ecological Site Descriptions (ESD).
Plant Communities and Transitional Pathways
A STM for the Thin Loamy ecological site (44AA162MT) is depicted in Figure 1. Thorough descriptions of each state, transition, plant community, and pathway follow the model. This model is based on available experimental research, field observations, and interpretations by experts and is likely to change as knowledge increases.
Plant communities differ across the MLRA because of the naturally occurring variability in weather, soils, and aspect. The biological processes on this site are complex; therefore, representative values are presented in a land management context. The species lists are representative and are not botanical descriptions of all species occurring, or potentially occurring, on this site. The species lists are not intended to cover every situation or the full range of conditions, species, and responses for the site.
Both percent species composition by weight and percent canopy cover are used in this ESD. Most observers find it easier to visualize or estimate percent canopy for woody species (trees and shrubs). Canopy cover drives the transitions between communities and states because of the influence of shade and interception of rainfall. Species composition by dry weight remains an important descriptor of the herbaceous community and of the community as a whole. Woody species are included in species composition for the site. Calculating similarity index requires use of species composition by dry weight.
This STM includes only native communities and states. The converted communities are described in the Ecological Dynamics section above.
State and transition model
Figure 2. 44AA Thin Loamy
More interactive model formats are also available.
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More interactive model formats are also available.
View Interactive Models
Click on state and transition labels to scroll to the respective text
State 1 submodel, plant communities
State 2 submodel, plant communities
State 3 submodel, plant communities
State 4 submodel, plant communities
State 1
Taller Bunchgrass State
This state is characterized by cool-season bunchgrasses and is represented by three communities that differ mainly in the percent composition of bluebunch wheatgrass and woody canopy cover (predominantly Wyoming big sagebrush). Forbs are a minor component in this state.
Community 1.1
Reference Plant Community - Bluebunch Wheatgrass Community
Figure 3. 44AA Thin Loamy 2
Figure 4. 44AA Thin Loamy 3
Figure 5. 44AA Thin Loamy 1
Bluebunch wheatgrass, a taller cool-season bunchgrass, dominates the Bluebunch Wheatgrass Community (1.1), with needleandthread as the subdominant grass and with a minor forb and shrub component. Bluebunch wheatgrass is typically the dominant species in the Bluebunch Wheatgrass Community (1.1). Many common forb species exist on this site, including western yarrow (Achillea millefolium) and bigseed biscuitroot (Lomatium macrocarpum). Shrub species, predominately fringed sagewort (Artemisia frigida) and Wyoming big sagebrush, are present as a minor part of the community. The Taller Bunchgrass State occurs generally on the Thin Loamy site in areas where proper grazing management practices have been implemented over a long period. The Bluebunch Wheatgrass Community (1.1) can be maintained through the implementation of properly managed grazing that provides adequate growing-season deferment to allow establishment of taller grass propagules and/or the recovery of vigor of stressed plants. The Bluebunch Wheatgrass Community (1.1) in general is resistant to change with proper grazing management, fire, or brush control and near normal precipitation. However, bluebunch wheatgrass lacks resistance to grazing during the spring growing season. It may decline in vigor and production if grazed in the spring more than one year in three (Wilson et al. 1960). Under continued growing season pressure, bluebunch wheatgrass will decrease in vigor. Needleandthread and sagebrush will fill in the vegetation gaps. This decrease drives the community shift to the Mixed Bunchgrass Community (1.2). The Bluebunch Wheatgrass Community (1.1) is moderately resilient to shrub invasion if properly managed. However, if continuous overgrazing occurs, shrub canopy will increase and desirable understory will decrease. There will be a notable increase in more grazing tolerant plants such as needleandthread and shortgrasses. When this occurs the Bluebunch Wheatgrass Community (1.1) will shift to a Mixed Bunchgrass Community (1.2). Once the site becomes dominated by needleandthread it will transition to the Altered State (2). Periodic fire increases the resilience of the Bluebunch Wheatgrass Community (1.1) by reducing competition and canopy cover of woody species. Fire also removes decedent herbaceous material, particularly from taller bunchgrasses, which promotes increased vigor and seedling establishment. Timing and intensity of a fire are critical components that can have varying positive or negative effects on this plant community. Fire does increase risk of invasion from invasive species, most notably cheatgrass. At least two growing seasons of rest are recommended to allow plants to recover after fire. Without fire and/or brush control, woody species on the site will increase and the site will shift to the Shrubland Community (1.3). This can occur with or without the degradation of the herbaceous community from bluebunch wheatgrass dominated to a community dominated by needleandthread. If degradation of the herbaceous component does occur, the site will transition to the Altered State (2). Because the woody species that dominate in the Shrubland Community (1.3) are native species in the Taller Bunchgrass State (1), the shift to the Shrubland Community (1.3) is a linear process with shrubs starting to increase soon after fire or brush control ceases. Heavy continuous grazing will reduce plant cover, litter, and mulch. Bare ground will increase and expose the soil to erosion. Litter and mulch will move off-site as plant cover declines. When canopy cover decreases to below 50%, the surface horizon becomes less stable and erosion can occur. This will make it more difficult to reestablish bluebunch wheatgrass plants due to decreased soil fertility. When overgrazing continues, invasive weedy grass and forb species move into the plant community and the site transitions to the Altered State (2), Sparsely Vegetated State (3) or the Invaded State (4). Until the Bluebunch Wheatgrass Community (1.1) crosses the threshold into the Altered State (2.1), Sparsely Vegetated Community (3.1) or the Invaded Community (4.1), this community can be managed back toward the Bluebunch Wheatgrass Community (1.1) using management practices including prescribed grazing, prescribed burning, and strategic weed control. It may take several years to achieve this state, depending upon the climate and the aggressiveness of the treatment. While the Bluebunch Wheatgrass Community (1.1) is resilient to degradation under proper management, the community remains at risk of invasion by aggressive non-native species because of the ability of spotted knapweed, leafy spurge, and cheatgrass to invade healthy rangelands and the widespread presence of propagules. Healthy plant communities are most resilient to invasives although many examples exist of well-managed areas that have been invaded by spotted knapweed. Invasives may impact this plant community even if the site does not yet have a critical population of invasives. Almost all reference sites had at least trace amounts of spotted knapweed and/or cheatgrass. It is believed that most sites with only trace amounts have been chemically treated for invasives at some point. These treatments would have impacted other broad-leafed species (forbs and shrubs). It is likely that this site had more potential for forb and shrub production than found on current reference sites. The natural fire regime would have favored an increase in forbs while maintaining shrubs as a minor component. Rock cover on the soil surface is minimal and does not impact productivity of this site. Plant basal cover is expected to be about 15 to 25% and bare ground is expected to be between 10-20%. Soil stability of this site is less stable than a site with a mollic epipedon do to the lack of organic matter and soil development. Signs of current erosion occurring on the site should be minimal to none. The following production figures do not represent the lowest or highest possible production for the reference community (1.1). For example, the high figure is not the most production that can occur in a wet year in the most mesic portion of the LRU. These values represent the range of variability for each species across the extent of the ecological site. Usually, values in the low production column represent production at the dry end of the LRU and those in the high production column represent production at the wet end of the LRU. Even the most stable communities exist within a range of dynamic equilibrium of species composition. The following table shows an example of species composition; the example is not the only mix of species possible in the Bluebunch Wheatgrass Community (1.1).
Figure 6. Annual production by plant type (representative values) or group (midpoint values)
Table 5. Annual production by plant type
| Plant type | Low (lb/acre) |
Representative value (lb/acre) |
High (lb/acre) |
|---|---|---|---|
| Grass/Grasslike | 595 | 808 | 1020 |
| Forb | 70 | 95 | 120 |
| Shrub/Vine | 35 | 47 | 60 |
| Total | 700 | 950 | 1200 |
Figure 7. Plant community growth curve (percent production by month). MT0441, 44A - Uplands. Includes all upland sites in 44A.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| J | F | M | A | M | J | J | A | S | O | N | D |
| 10 | 25 | 35 | 15 | 10 | 5 |
Community 1.2
Mixed Bunchgrass Community
Bluebunch wheatgrass and needleandthread share dominance in this community. There may be a moderate overstory of Wyoming big sagebrush. Needleandthread and Wyoming big sagebrush increase in species composition when bluebunch wheatgrass decreases because of improper grazing management and lack of fire and brush control. Bluebunch wheatgrass will have lower relative production and lower total production than in the Bluebunch Wheatgrass Community (1.1). Other grass species that are more tolerant to grazing and likely to increase compared to the Reference Plant Community include Sandberg bluegrass (Poa secunda), prairie junegrass (Koeleria macrantha), and western/thickspike wheatgrass (Pascopyrum smithii, Elymus trachycaulus). Some increaser forbs species include western yarrow, hoods phlox (Phlox hoodii), scarlet globemallow (Sphaeralcea coccinea), hairy goldenaster (Heterotheca villosa), and pussytoes (Antennaria spp.). Fringed sagewort is a shrub that also increases under prolonged drought or heavy grazing. Heavy continuous grazing will reduce plant cover, litter, and mulch. Bare ground will increase and expose the soil to erosion. Litter and mulch will move off-site as plant cover declines. As long as the canopy cover remains > 50% and production of bluebunch wheatgrass is < 10% of total biomass production, the site can return to the Taller Bunchgrass Community (Pathway 1.2A). The Mixed Bunchgrass (1.2) and the Shrubland Community (1.3) are “At-Risk” Communities. The transition to the Altered State (2) can occur from any community within the Taller Bunchgrass State (1), it is not dependant on an increase of woody canopy cover, but on the decrease of bluebunch wheatgrass composition to < 10%. When overgrazing continues, increaser species such as Sandberg and native forb species will become more dominate and this triggers the transition from the Taller Bunchgrass State (1). Fire and/or brush control can be used to maintain the site in the Taller Bunchgrass State (1) as long as bluebunch wheatgrass production does not fall below 10%. Until the Mixed Bunchgrass Community (1.2) crosses the threshold into the Altered State (2.0), this community can be managed back toward the Bluebunch Wheatgrass Community (1.1) using management practices including prescribed grazing combined with prescribed burning and strategic brush control. It may take several years to make this shift, depending upon weather and aggressiveness of grazing management and brush treatment. Fire can be used to control smaller shrubs and trees. Chemical or mechanical treatment of larger shrubs and trees may be necessary in older stands. Without any form of brush control, woody species continue to increase in canopy cover. Once woody canopy exceeds approximately 20% and attains reproductive capability, a shift to the Shrubland Community (1.3) has occurred.
Community 1.3
Shrubland Community
The Shrubland Community (1.3) is characterized by > 20% woody canopy cover with bluebunch wheatgrass in the understory. Once woody canopy cover reaches 20%, the site will begin to take on the appearance of a shrubland. The dominant shrub species in this community is Wyoming big sagebrush, while the understory is dominated by bluebunch wheatgrass. Other common shrub species include fringed sage, rubber rabbitbrush (Ericameria nauseosa), yellow rabbitbrush (Chrysothamnus viscidiflorus), and Woods' rose (Rosa woodsii). Without fire, woody canopy cover increases and the Mixed Bunchgrass Community (1.2) shifts to the Shrubland Community (1.3). The Shrubland Community (1.3) differs from the Altered Shrubland Community (2.2) in the amount of degradation present in the understory. Under proper grazing management, the herbaceous component will be dominated by bluebunch wheatgrass. As long as bluebunch wheatgrass has not fallen below 10% species composition, the Shrubland Community (1.3) can be managed back to the Bluebunch Community (1.1) using prescribed grazing and strategic weed control. It may take several years to achieve this recovery, depending on growing conditions, vigor of remnant bluebunch wheatgrass plants, and the aggressiveness of the weed treatments. With improper grazing management, bluebunch wheatgrass will decline and less palatable grass species, such as needleandthread and forb species will dominate understory and the site transitions to the Altered State (2).
Pathway 1.1A
Community 1.1 to 1.2
The Bluebunch Wheatgrass Community (1.1) requires fire and/or brush control to maintain woody species cover below 10%. This community will shift to the Mixed Bunchgrass Community (1.2) without fire or brush control. Native woody species canopy exceeding 10% indicate a transition to the Mixed Bunchgrass Community (1.2). The Bluebunch Wheatgrass Community (1.1) can be maintained through the implementation of brush management combined with properly managed grazing that provides adequate growing-season deferment to allow establishment of bluebunch wheatgrass propagules and/or the recovery of vigor of stressed plants. The driver for this community pathway is improper grazing management in combination with lack of fire and/or brush control.
Pathway 1.2A
Community 1.2 to 1.1
The Mixed Bunchgrass Community (1.2) will return to the Bluebunch Wheatgrass Community (1.1) with brush control and proper grazing management that provides sufficient critical growing-season deferment in combination with proper grazing intensity. Favorable moisture conditions will facilitate or accelerate this transition. Reduction of the woody component will require inputs of fire and/or brush control. The driver for this community pathway is proper grazing management in combination with fire and/or brush control.
Pathway 1.2B
Community 1.2 to 1.3
Shrubs make up a portion of the plant community in the Bluebunch Wheatgrass Community, hence woody propagules are present. Therefore, the Taller Bunchgrass State is always at risk for shrub dominance and a shift to the Shrubland Community (1.3) in the absence of fire and brush management. The drivers for Community Shift 1.2B are overgrazing and lack of fire and/or brush control. The mean fire return interval in the Taller Bunchgrass State is likely less than 35 years. Even with proper grazing and favorable climate conditions, lack of fire or brush control for 20 years will allow shrubs and trees to increase in canopy to reach the 20% threshold level. Improper grazing, prolonged drought, and a warming climate will provide a competitive advantage to shrubs, which will accelerate this process. The driver for this community shift is improper grazing management in combination with lack of fire and/or brush control.
Pathway 1.3B
Community 1.3 to 1.1
The Shrubland Community can return to the Bluebunch Wheatgrass Community after a fire as long as the understory is able to carry the fire and bluebunch wheatgrass crowns survive the fire and re-sprout and/or there is a sufficient seed for bluebunch wheatgrass to re-vegetate the area.
Pathway 1.3A
Community 1.3 to 1.2
The Shrubland Community can return to the Mixed Bunchgrass Community after a fire as long as the understory is able to carry the fire and bluebunch wheatgrass crowns survive the fire and re-sprout and/or there is a sufficient seed for bluebunch wheatgrass to re-vegetate the area.
State 2
Altered State
This state is characterized by having to < 10% bluebunch wheatgrass and < 50% canopy cover. State 2 is represented by two communities that differ in the percent canopy cover of woody species. Production in this state is considerably lower than in the Taller Bunchgrass State (1). Some native plants tend to increase under prolonged drought and/or heavy grazing practices. A few of these species may include prairie junegrass, Sandberg bluegrass, western yarrow, scarlet globemallow, hairy goldenaster, and fringed sagewort.
Community 2.1
Needleandthread Community
The Needleandthread Community (2.1) is characterized by an herbaceous component dominated by Needleandthread with bluebunch wheatgrass being less than 10% of species composition by dry weight. This makes it difficult for bluebunch wheatgrass to increase with simply a change in grazing management alone. This community may or may not have a shrub component with canopy cover up to 20%. If a shrub component is present, it will most likely be dominated by Wyoming big sagebrush. The Needleandthread Community tends to occur if the forage component has been degraded but fire or brush control has kept the shrub community to less than 20 % cover. This community is at risk of shifting to the Altered Shrubland Community (2.2) if without fire or other brush control. This shift can be accelerated when improper grazing management occurs. This most often happens when stocking rates are not adjusted to compensate for the decrease in forage production as shrub production increases. Canopy cover will likely be less than 50%. Wind and water erosion may erode soil from plant interspaces. Soil fertility is reduced, soil compaction is increased, and resistance to soil surface erosion has is less than in the Taller Bunchgrass State (1).
Community 2.2
Altered Shrub Community
The Altered Shrubland Community (2.2) is characterized by < 20% woody canopy cover with needleandthread or shortgrasses in the understory. It has the appearance of shrub dominance with a degraded understory. The overstory is similar to the Shrubland Community (1.3) in the Taller Bunchgrass State (1). Wyoming big sagebrush typically dominates the shrub component but rabbitbrush and/or Woods’ rose may share dominance. The understory in the community can be dominated by needleandthread to an understory dominated by forbs and shortgrasses. Failure to adjust stocking rate as shrub cover increases results in further degradation of the herbaceous community causing an increase in bare ground between shrubs. This community can have a dense canopy of shrubs with sparse understory making it difficult to return to the Needleandthread Community or a community within the Taller Bunchgrass, even if brush is removed. Reseeding and other cultural practices may be needed. When overgrazing continues, invasive grass and forb species move into the plant community and the site can transition to the Sparsely Vegetated State (3) or the Invaded State (4). Until the Altered Shrubland Community (2.2) crosses the threshold into the Sparsely Vegetated State (3) or the Invaded State (4) this community can be managed toward the Needleandthread Community (2.1) using prescribed grazing and strategic weed control.
Pathway 2.1A
Community 2.1 to 2.2
The Altered State is always at risk for shrub dominance and a shift to the Altered Shrubland Community (2.2) in the absence of fire and brush management. The drivers for Community Shift 2.1A are overgrazing and lack of fire and/or brush control. The mean fire return interval in the Altered State is likely less than 35 years. Even with proper grazing and favorable climate conditions, lack of fire or brush control for 20 years will allow shrubs and trees to increase in canopy to reach the 20% threshold level. Improper grazing, prolonged drought, and a warming climate will provide a competitive advantage to shrubs, which will accelerate this process. The driver for this community shift is improper grazing management in combination with lack of fire and/or brush control.
Pathway 2.2A
Community 2.2 to 2.1
The Altered Shrubland Community (2.2) can return to the Needleandthread Community (2.1) after a fire if the growing conditions are adequate for needleandthread.
State 3
Sparsely Vegetated State
The single community described below characterizes this state.
Community 3.1
Sparsely Vegetated Community
Long-term grazing mismanagement with continuous growing-season pressure will reduce total productivity of the site and lead to an increase of bare ground. Once plant cover is reduced, the site is more susceptible to erosion. Soil erosion reduces soil fertility creating a reduction in plant production. This soil erosion or loss of soil fertility indicates the transition to the Sparsely Vegetated State (3). The decline may be exacerbated by extended drought conditions. Very sparse plant cover and soil surface erosion characterize this community. Canopy cover may be very sparse or clumped (canopy cover to < 25%). Weeds, annual species, or shortgrass species dominate the plant community. Mid-stature perennial bunchgrass species (e.g., needleandthread) may exist, but only in patches. This community has crossed a threshold (T1B, T2A) compared to the Taller Bunchgrass State (1) and compared to the Altered State (2) due to the erosion of soil, loss of soil fertility, or degradation of soil properties. If further soil erosion occurs, there will be a critical negative shift in the ecological processes of this site. The effects of soil erosion can alter the hydrology, soil chemistry, soil microorganisms, and soil physics to the point where intensive restoration is required to restore the site to another state or community. Simply changing grazing management cannot create sufficient change to restore the site within a reasonable period. It will require a considerable input of energy to move the site back to the Taller Bunchgrass State (1). This state has lost soil or vegetation attributes to the point that recovery to the Taller Bunchgrass State (1) will require reclamation efforts, i.e., soil rebuilding, intensive mechanical treatments, and/or reseeding. In this community there may be a significant amount of bare ground, and large gaps may occur between plants. The transition to this state could occur because of overgrazing (often because of failure to adjust stocking rates in response to declining forage production because of increased dominance of unpalatable invasive species), long-term lack of fire, warming climate, or extensive drought. Potential exists for soils to erode to the point that irreversible damage may occur. If herbaceous cover decreases to the point that soils are no longer stable, the shrub overstory may not prevent soil erosion. This plant community may be in a terminal state that will not return to the reference state because of degraded soil properties and loss of higher successional native plant species.
State 4
Invaded State
The single community described below characterizes this state.
Community 4.1
Invaded Community
The Invaded State (4) is characterized by > 25% of invasive species. Spotted knapweed, leafy spurge, sulphur cinquefoil, and/or cheatgrass are the dominant invasive species in MLRA 44A. Introduced exotic plant species have been identified as one of the greatest threats to the integrity and productivity of native rangeland ecosystems and conservation of indigenous biodiversity (DiTomaso 2000; Mack et al. 2000). In addition to environmental consequences, the damages caused and the costs incurred to control invasive plants are several billion dollars each year in the United States (Pimentel et al. 2000). Invasives are the driving factor throughout western Montana and a focal part of the ecology of MLRA 44A. Their ability to take over and dominate a site has become a big concern. Improper grazing management has contributed to the spread of these species. The potential for altered ecosystem structure and function is high in the Invaded State (4) and can occur in many ways. The increase in invasive species, especially noxious weeds, can lead to a reduction of the native bunchgrasses and an increase in the proportion of bare ground, which often results in reduced infiltration rates and increased surface runoff and erosion. Invasion by cheatgrass reduces above and below ground biomass (Ogle et al. 2003), increases plant litter, changes plant community canopy architecture (Belnap and Phillips 2001), reduces soil biota richness and abundance, reduces plant community richness (Belnap et al. 2005), increases wildfire frequency (Whisenant 1990), and potentially facilitates invasion by other noxious or invasive plants. Dense populations of invasive species can cause soil loss to increase because of lack of surface cover (Lacey et al. 1989). Early in the invasion process there is a lag phase where invasive plant populations remain small and localized before expanding exponentially (Hobbs and Humphries 1995). Based on research conducted in noxious weed-invaded plant communities in Montana, it is reasonable to estimate that 25% dry-weight composition of invasive plant species is the point in the invasion process where spread and abundance increase exponentially and where a plant community crosses a threshold (Masters and Sheley 2001). For aggressive invasive species (i.e., spotted knapweed), this threshold may be 10% or less. The site becomes “At Risk” as soon as the first individual plant of aggressive invasives reaches reproductive capacity. Once invasive species dominate the site, either in species composition by weight or in their impact on the community, the threshold has been crossed to the Invaded State (4). Once invasive become established, they are very difficult to eradicate. Therefore, considerable effort should be placed in preventing plant communities from crossing a threshold to the Invaded State (4) through early detection and proper weed management. Preventing new invasions is by far the most cost-effective control strategy and typically places an emphasis on education. Control measures used on the noxious plant species impacting this ecological site include chemical, biological, and cultural control methods. The best success has been found with an integrated weed management strategy that incorporates one or several of these options along with education and prevention efforts (DiTomaso 2000). Production in the invaded community may vary greatly. A site dominated by spotted knapweed, where soil fertility and chemistry remain near potential may have production near that of the reference community. A site with degraded soils and infestation of cheatgrass may produce only 10-20% as many pounds per acre of the reference community. Invasive plant species have effective reproductive strategies, long seed viability in the soil seed bank, and/or allelopathic properties (Williamson and Fitter 1996). Spotted knapweed has allelopathic properties whereby its roots exude catechin, which may limit the growth and establishment of other plant species (Callaway and Vivanco 2007; Bais et al. 2002), thus promoting its own success. An in-vitro experiment showed that other weeds like Dalmatian toadflax (Linaria dalmatica), kochia (Kochia scoparia), diffuse knapweed (Centaurea diffusa), and crops, such as wheat (Triticum aestivum), showed mortality on the fourteenth day after addition of root exudates from spotted knapweed (Bais et al. 2002). This allelopathic property creates highly resilient communities. Cheatgrass has the ability to rapidly establish and attain community dominance following disturbances such as wildfire (Young and Evans 1978) or other disturbances creating bare soil. Cheatgrass is a successful invader because it has the ability to rapidly respond to increases in resource availability (Norton et al. 2004 and Lowe et al. 2003) as well as to compete for water (Pellant 1996). Cheatgrass was introduced into the United States in packing materials, ship ballast, and likely as a contaminant of crop seed. Cheatgrass was first found in the United States near Denver, Colorado in the late 1800s. In the late 1800s and early 1900s, it spread explosively in the ready-made seedbeds prepared by the trampling livestock hooves of overstocked rangelands. Cheatgrass has developed into a severe weed in several agricultural systems throughout North America, particularly western pastureland, rangeland, and winter wheat fields (NRCS 2009). Today, cheatgrass is found in most of the western states having reached its range of current distribution by 1930. In fact, a survey of 11 western states showed that cheatgrass was present on at least 60 million acres (Pellant 1996). After arriving in 1893 on the San Juan Islands of Washington, spotted knapweed had established in over 24 counties in three northwestern states by 1924, with several large infestations near Missoula, Montana (Sheley et al. 2005). By 1975, spotted knapweed had spread into most western counties of Montana, and, today, it is found in every county in Montana. Leafy spurge, a native to Eurasia, was sighted in Park County, Montana as early as 1925 and has since been found in every Montana County. Overgrazing by livestock has contributed to the spread of leafy spurge (Sheley et al. 2005).
Transition T1A
State 1 to 2
The Taller Bunchgrass State (1) transitions to the Altered State (2) if bluebunch wheatgrass falls below 10% species composition. The trigger for this transition is the loss of taller bunchgrasses, which creates a shift in species composition towards lower productive species, especially needleandthread. This transition can occur from any community within the Taller Bunchgrass State (1), it is not dependant on an increase of woody canopy cover, but on the decrease of bluebunch wheatgrass production. The driver for this transition is improper grazing management and/or long-term drought leading to a decrease in bluebunch wheatgrass composition to < 10%.
Transition T1B
State 1 to 3
The Taller Bunchgrass State (1) transitions to the Sparsely Vegetated State (3) if plant canopy cover declines to < 25% and bluebunch wheatgrass decreases to below 10% by dry weight. The trigger for this transition is the loss of taller bunchgrasses, which creates open spots of bare soil. Soil erosion is accompanied by decreased soil fertility driving transitions to the Sparsely Vegetated State. There are several other key factors signaling the approach of transition T1B: increases in soil physical crusting, decreases in cover of cryptogamic crusts, decreases in soil surface aggregate stability, and/or evidence of erosion, including water flow patterns, development of plant pedestals, and litter movement. The driver for this transition is improper grazing management and/or long-term drought leading to a decrease in rough fescue composition to < 10%.
Transition T1C
State 1 to 4
Regardless of grazing management, without some form of weed management (chemical, mechanical, or biological control), the Taller Bunchgrass State (1) can transition to the Invaded State (4) if aggressive invasive species, such as spotted knapweed and cheatgrass are introduced, even if the herbaceous component of the reference community is thriving. Healthy plant communities are most resilient to invasives. Long-term stress conditions for native species (e.g., overgrazing, drought, and fire) accelerate the process. If populations of invasive species reach critical levels, the site transitions to the Invaded State. The driver for this transition is the presence of aggressive invasive species.
Restoration pathway R2A
State 2 to 1
Restoration of the Altered State to the Taller Bunchgrass State requires substantial energy input. The drivers for this restoration pathway are removal of woody species, restoration of native herbaceous species by reseeding bluebunch wheatgrass.
Transition T2A
State 2 to 3
Removal of shrubs without proper grazing management can lead to an increase in bare ground and erosion of the fertile surface horizon and the site can degrade to the Sparsely Vegetated State (3). The driver for this transition is brush management without proper grazing management.
Transition T2B
State 2 to 4
Removal of shrubs can lead to an increase in bare ground. If invasive species are present, bare ground offers opportunity for invasive species to fill open areas, leading to the Invaded State (4). The driver for this transition is brush management in presence of invasive species.
Restoration pathway R3A
State 3 to 1
The Sparsely Vegetated State (3) has lost soil or vegetation attributes to the point that recovery to the Taller Bunchgrass State (1) will require reclamation efforts such as soil rebuilding, intensive mechanical treatments, and/or revegetation. The drivers for this restoration pathway are reclamation efforts and proper grazing management. The trigger is restoration efforts.
Restoration pathway R3B
State 3 to 2
The Sparsely Vegetated State (3) has lost soil or vegetation attributes to the point that recovery to the Altered State (2) will require reclamation efforts such as soil rebuilding, intensive mechanical treatments, and/or reseeding in recommended areas only. If the reclamation efforts are performed without reseeding bluebunch wheatgrass, under unfavorable climatic conditions, or without proper grazing management, the site will return to the Altered State.
Transition T3A
State 3 to 4
Invasive species can occupy Sparsely Vegetated State (3) and drive it to the Invaded State (4). The Altered Bunchgrass State is at risk of this transition occurring if invasive propagules are present. The driver for this transition is the presence of critical population levels (> 25%) of invasive species. The trigger is the presence of propagules of invasive species.
Restoration pathway R4A
State 4 to 1
Restoration of the Invaded State (4) to the Taller Bunchgrass State (1) requires substantial energy input. The drivers for this restoration pathway are removal of invasive species, restoration of native bunchgrass species, ongoing management of invasives, and proper grazing management. Without maintenance, invasive species are likely to return (probably rapidly) because of the presence of propagules in the soil, increases in soil disturbance. The drivers for this reclamation pathway are treatments to reduce or remove invasive/noxious species in combination with favorable growing conditions. The trigger is invasive species control.
Restoration pathway R4B
State 4 to 2
Weed management without reseeding desirable, taller bunchgrasses, favorable climatic conditions, or proper grazing management will lead to the Altered State (2).
Restoration pathway R4C
State 4 to 3
If invasive species are removed without sufficient remnant populations of reference community species (particularly rough fescue), a site in the Invaded State (4) is likely to return to the Sparsely Vegetated State (3) instead of the Taller Bunchgrass State (1). The driver for the reclamation pathway is weed management without reseeding. The trigger is invasive species control.
Additional community tables
Table 6. Community 1.1 plant community composition
| Group | Common name | Symbol | Scientific name | Annual production (lb/acre) | Foliar cover (%) | |
|---|---|---|---|---|---|---|
|
Grass/Grasslike
|
||||||
| 1 | Cool Season Bunchgrasses | 525–900 | ||||
| bluebunch wheatgrass | PSSP6 | Pseudoroegneria spicata | 490–840 | – | ||
| needle and thread | HECO26 | Hesperostipa comata | 210–360 | – | ||
| green needlegrass | NAVI4 | Nassella viridula | 70–120 | – | ||
| 2 | Shortgrasses/Rhizomatous Grasses/Grasslikes | 70–120 | ||||
| Grass, perennial | 2GP | Grass, perennial | 35–60 | – | ||
| sedge | CAREX | Carex | 35–60 | – | ||
| thickspike wheatgrass | ELLA3 | Elymus lanceolatus | 35–60 | – | ||
| prairie Junegrass | KOMA | Koeleria macrantha | 35–60 | – | ||
| western wheatgrass | PASM | Pascopyrum smithii | 35–60 | – | ||
| Sandberg bluegrass | POSE | Poa secunda | 35–60 | – | ||
|
Forb
|
||||||
| 3 | Forbs | 70–120 | ||||
| Forb, annual | 2FA | Forb, annual | 35–60 | – | ||
| Forb, perennial | 2FP | Forb, perennial | 35–60 | – | ||
| common yarrow | ACMI2 | Achillea millefolium | 35–60 | – | ||
| onion | ALLIU | Allium | 35–60 | – | ||
| aster | ASTER | Aster | 35–60 | – | ||
| milkvetch | ASTRA | Astragalus | 35–60 | – | ||
| narrowleaf blue eyed Mary | COLI | Collinsia linearis | 35–60 | – | ||
| bastard toadflax | COUM | Comandra umbellata | 35–60 | – | ||
| fleabane | ERIGE2 | Erigeron | 35–60 | – | ||
| buckwheat | ERIOG | Eriogonum | 35–60 | – | ||
| hairy false goldenaster | HEVI4 | Heterotheca villosa | 35–60 | – | ||
| flax | LINUM | Linum | 35–60 | – | ||
| desertparsley | LOMAT | Lomatium | 35–60 | – | ||
| beardtongue | PENST | Penstemon | 35–60 | – | ||
| phlox | PHLOX | Phlox | 35–60 | – | ||
| Missouri goldenrod | SOMI2 | Solidago missouriensis | 35–60 | – | ||
| scarlet globemallow | SPCO | Sphaeralcea coccinea | 35–60 | – | ||
|
Shrub/Vine
|
||||||
| 4 | Shrubs | 35–60 | ||||
| Shrub (>.5m) | 2SHRUB | Shrub (>.5m) | 18–30 | – | ||
| prairie sagewort | ARFR4 | Artemisia frigida | 18–30 | – | ||
| Wyoming big sagebrush | ARTRW8 | Artemisia tridentata ssp. wyomingensis | 18–30 | – | ||
| yellow rabbitbrush | CHVI8 | Chrysothamnus viscidiflorus | 18–30 | – | ||
| rubber rabbitbrush | ERNA10 | Ericameria nauseosa | 18–30 | – | ||
Interpretations
Animal community
Livestock grazing is suitable on this site due to the potential to produce high quality forage. This site may be preferred for grazing by livestock, and animals may congregate in these areas, however if slopes are > 15% and distance from water is too great, livestock grazing will be limited. Management objectives should include maintenance or improvement of rangeland health attributes of this ecological site. Careful management of timing, intensity and duration of grazing to minimize grazing re-growth and providing adequate rest is important. Shorter grazing periods and changing season of use during the growing season are recommended for plant maintenance, health and recovery.
Continuous grazing with improper stocking rates throughout the growing season in pastures year after year will be detrimental, will alter the plant composition and production over time, and will result in a transition to the Mixed Bunchgrass Community (1.2) or the Shrubland Community (1.3) or potentially hasten a change to the Invaded State (4). Transition to other states will depend on how well the site is managed over time with grazing animals as well as other circumstances such as weather conditions over a period of time.
The transition to the Mixed Bunchgrass Community (1.2) or the Shrubland Community (1.3) can be the result of long-term, continuous grazing and/or repeated critical growing season grazing (early season grazing during stem elongation). This transition can also occur due to a combination of overgrazing and drought. Repeated grazing during stem elongation (generally mid-April through mid-June), can have detrimental affects, especially on the taller key bunchgrass species. Repeated spring grazing and/or repeated and prolonged summer grazing depletes stored carbohydrates, resulting in poor vigor of key forage plants over time and eventual death of these cool-season grasses – this can lead to an increase in less desirable native species and/or noxious weeds.
The Mixed Bunchgrass Community (1.2) and the Shrubland Community (1.3) can occur across the entire ecological site or can occur in a mosaic with higher and/or lower states. This is most notable in areas that attract additional grazing, such as water sources or salting locations.
The Mixed Bunchgrass Community (1.2) or the Shrubland Community (1.3) is subject to further degradation to the Altered State (2), the Sparsely Vegetated State (3) or the Invaded State (4). Management should focus on grazing management strategies that will prevent further degradation. Forage quantity and/or quality may be substantially reduced compared to the Reference Plant Community.
In the Altered State, forage production is substantially reduced compared to the Taller Bunchgrass State. Grazing is possible in the Sparsely Vegetated State and the Invaded State, but forage production is greatly reduced in both states. Grazing should be carefully managed to avoid soil loss and degradation of soil properties as well as to ensure adequate livestock health.
Prescriptive grazing should be included in a conservation plan to maintain vigor of key native plant species while targeting the invasive species problem. In some instances, carefully targeted grazing (sometimes in combination with other treatments) can reduce or eliminate populations of invasive species.
Distance to drinking water and slope can reduce grazing capacity within a management unit. Adjustments should only be made for the area that is considered necessary for reduction of animal numbers. For example 30% of a management unit may have 25% slopes and distances of > 1 mile from water; therefore the adjustment is only calculated for 30% of the unit (50% reduction on 30% of management unit). The table below is a general guide for ranches in Montana (Ricketts et al. 2004). Fencing, slope length, management, access, terrain and breeds are all factors that can increase or decrease the percent of grazable acres within a management unit. Adjustments should be made that incorporate pasture conditions when calculating stocking rates.
Hydrological functions
The water cycle functions best in the Taller Bunchgrass State (1) but infiltration is low on the Thin Loamy Site. The water cycle degrades as the vegetation community declines. With total ground cover averaging around 85%, raindrop impact on the soil surface is reduced, which keeps erosion and sedimentation transport low. Water leaving the site will have minimal sediment load, which allows for high water quality in associated streams. The Bluebunch Wheatgrass Community (1.1) should have no rills or gullies present and drainageways should be vegetated and stable.
Improper grazing management results in the transition to the Altered State (2). This state has reduced canopy cover, and increased bare ground. Therefore, infiltration is reduced and runoff increased due to reduced ground cover, rainfall splash, soil capping, reduced organic matter, and poor structure.
In the Sparsely Vegetated State (3) and the Invaded State (4) canopy and ground cover are greatly reduced compared to the Taller Bunchgrass State (1), which impairs the water cycle. Infiltration will greatly decrease and runoff will increase because of reduced ground cover, rainfall splash, soil capping, reduced organic matter, and poor structure. Sparse ground cover and decreased infiltration can combine to increase frequency and severity of flooding within a watershed. Soil erosion is accelerated, quality of surface runoff is poor, and sedimentation increases.
Recreational uses
This site provides some limited recreational opportunities for hiking, horseback riding, and big game and upland bird hunting. The forbs have flowers that appeal to photographers. This site provides valuable open space.
Wood products
None
Other products
None
Other information
None
Supporting information
Other references
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Arno, S. F., and Gruell, G. E. 1986. Douglas-fir encroachment into mountain grasslands in southwestern Montana. Journal of Range Management 39(3): 272-275.
Bais, H. P., T. S. Walker, F. R. Stermitz, R. H. Hufbauer, and J. M. Vivanco. 2002. Enantiomeric-dependent phytotoxic and antimicrobial activity of (±)-catechin. A rhizosecreted racemic mixture from spotted knapweed. Plant Physiology 128: 1173-1179.
Belnap, J., and S. L. Phillips. 2001. Soil biota in an ungrazed grassland: response to annual grass (Bromus tectorum) invasion. Ecological Applications 11:1261-1275.
Belnap, J., S. L. Phillips, S. K. Sherrod, and A. Moldenke. 2005. Soil biota can change after exotic plant invasion: does this affect ecosystem processes? Ecology 86:3007-3017.
Bestelmeyer, B., and J. R. Brown. 2005. State-and-transition models 101: a fresh look at vegetation change. The Quivira Coalition Newsletter, Vol. 7, No. 3.
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Bestelmeyer, B., J. E. Herrick, J. R. Brown, D. A. Trujillo, and K. M. Havstad. 2004. Land management in the American Southwest: a state-and-transition approach to ecosystem complexity. Environmental Management 34(1):38-51.
Callaway, R. M., and J. M. Vivanco. 2007. Invasion of plants into native plant communities using the underground information superhighway. Allelopathy Journal 19:143-151.
DiTomaso, J. M. 2000. Invasive weeds in rangelands: Species, impacts, and management. Weed Science 48:255-265.
Herrick, J. E., J. W. Van Zee, K. M. Havstad, L. M. Burkett, and W. G. Whitford. 2005. Monitoring manual for grassland, shrubland and savanna Ecosystems. Volume I Quick Start. USDA - ARS Jornada Experimental Range, Las Cruces, New Mexico.
Herrick, J. E., J. W. Van Zee, K. M. Havstad, L. M. Burkett, and W. G. Whitford. 2005. Monitoring manual for grassland, shrubland and savanna Ecosystems. Volume II: Design, supplementary methods and interpretation. USDA - ARS Jornada Experimental Range, Las Cruces, New Mexico.
Hobbs, R. J., and S. E. Humphries. 1995. An integrated approach to the ecology and management of plant invasions. Conservation Biology 9:761-770.
Lacey, J. R., C. B. Marlow, and J. R. Lane. 1989. Influence of spotted knapweed (Centaurea maculosa) on surface runoff and sediment yield. Weed Technology 3:627-631.
Launchbaugh, K. L., R. J. Daines, and J. W. Walker. [Eds.] 2006. Targeted grazing: a natural approach to vegetation management and landscape enhancement. Centennial, CO, USA: American Sheep Industry Association (available online at www.cnr.uidaho.edu/rx-grazing/Handbook.htm)
Lesica, P., and Cooper, S. V. 1997. Presettlement vegetation of southern Beaverhead County, Montana. Unpublished report to the State Office, Bureau of Land Management, and Beaverhead-Deerlodge National Forest. Montana Natural Heritage Program, Helena, MT. 35 pp.
Lowe, P. N., W. K. Laurenroth, and I. C. Burke. 2003. Effects of nitrogen availability on competition between Bromus tectorum and Bouteloua gracilis. Plant Ecology 167:247-254.
Mack, R. N., D. Simberloff, W. M. Lonsdale, H. Evans, M. Clout, and F. A. Bazzaz. 2000. Biotic invasions: causes, epidemiology, global consequences, bunchgrass ranges in southern Idaho. Journal of Range Management 24:407-410.
Masters, R. A., and R. L. Sheley. 2001. Principles and practices for managing rangeland invasive plants. Journal of Range Management 54: 502-517.
Norton, J. B., T. A. Monaco, J. M. Norton, D. A. Johnson, and T. A. Jones. 2004. Soil morphology and organic matter dynamics under cheatgrass and sagebrush-steppe plant communities. Journal of Arid Environments 57:445-466.
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NRCS. 2008. (electronic) Field Office Technical Guide. Available online at http://efotg.nrcs.usda.gov/efotg_locator.aspx?map=MT
NRCS. 2009. Plant Guide: Cheatgrass. Prepared by Skinner et al., National Plant Data Center.
Ogle, S., W. Reiners, and K. Gerow. 2003. Impacts of exotic annual brome grasses (Bromus spp.) on ecosystem properties of northern mixed grass prairie. Am. Midl. Nat 149:46-58.
Pellant, M. 1996. Cheatgrass: The invader of the West. Bureau of Land Management, Idaho State Office, 22 pp.
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Pimentel, D., L. Lach, R. Zuniga, and D. Morrison. 2000. Environmental and economic costs of nonindigenous species in the United States. Bioscience 50:53-65.
Pokorny, M. L., R. L. Sheley, C. A. Zabinski, R. E. Engel, A. J. Svejcar, and J. J. Borkowski. 2005. Plant functional group diversity as a mechanism for invasion resistance. Restoration Ecology 13(3): 1-12.
Ricketts, M. J., R. S. Noggles, and B. Landgraf-Gibbons. 2004. Pryor Mountain Wild Horse Range Survey and Assessment. USDA-Natural Resources Conservation Service.
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USDA/NRCS Soil survey manuals for appropriate counties within MLRA 44A.
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Approval
Kirt Walstad, 2/05/2022
Rangeland health reference sheet
Interpreting Indicators of Rangeland Health is a qualitative assessment protocol used to determine ecosystem condition based on benchmark characteristics described in the Reference Sheet. A suite of 17 (or more) indicators are typically considered in an assessment. The ecological site(s) representative of an assessment location must be known prior to applying the protocol and must be verified based on soils and climate. Current plant community cannot be used to identify the ecological site.
| Author(s)/participant(s) | W. Lujan, N. Svendsen, J. Alexander, K. Walstad, J. Siddoway, M. Hansen |
|---|---|
| Contact for lead author | NRCS Missoula Area Office |
| Date | 03/01/2010 |
| Approved by | Kirt Walstad |
| Approval date | |
| Composition (Indicators 10 and 12) based on | Annual Production |
Indicators
-
Number and extent of rills:
Slopes range from 15% to 50%. Rills are rare in the Taller Bunchgrass State on slopes between 15%-35%. On slopes >35%, plant cover, basal area and litter are generally reduced and narrow rills <5 feet long may be present. -
Presence of water flow patterns:
Water flow patterns are generally rare in the reference state. Following occasional (5 – 30 % probability), heavy thunderstorms and winter thaw events, short, sinuous, discontinuous flow patterns may be apparent. On the steeper slopes (>35%) water flow patterns may become more evident and there may be areas which show accumulations of litter due to water movement. -
Number and height of erosional pedestals or terracettes:
Very slight to slight on slopes <20%. Occasionally pedestals up to 0.5 inches may be encountered. As slopes increase pedestals may become more numerous and prominent. -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Bare ground is expected be between 10-20% - bare areas tend to be inconspicuous and not connected. -
Number of gullies and erosion associated with gullies:
Gullies should not occur in the Taller Bunchgrass State. If there is evidence of past erosion that has created gullies, these areas should be stabilized and have no active erosion. -
Extent of wind scoured, blowouts and/or depositional areas:
Appearance or evidence of these erosional features on the landscape would not be present on this site. -
Amount of litter movement (describe size and distance expected to travel):
Litter will be evident across this site representing organic debris from the vegetation of the functional/structural groups and will not move. A severe convection storm or a significant thaw event could cause litter to move short distances, especially on slopes greater than 6%. -
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Resistance to erosion will be high with soil stability values of 5 or 6; areas of bare soil on this site may have values between 3 and 5 if not under plant canopy. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Structure is granular at the soil surface. Organic matter is about 1.5%. The surface horizon is 3 to 6 inches thick. Mollic epipedon is not present. -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
The reference plant community (1.1) is dominated by bluebunch wheatgrass which will maximize infiltration and minimize runoff throughout the site. With the increase of needleandthread in Plant community (1.2) infiltration may decrease and runoff may increase but overall this plant community will have only slight affects on infiltration and runoff. -
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
A compaction layer would not be expected on this ecological site. A platy soil surface structure would indicate a departure from the reference state. -
Functional/Structural Groups (list in order of descending dominance by above-ground annual-production or live foliar cover using symbols: >>, >, = to indicate much greater than, greater than, and equal to):
Dominant:
Plant community 1.1 - Taller cool season bunchgrasses (bluebunch wheatgrass) >> mid-stature cool season bunchgrasses (needleandthread) > cool season rhizomatous grasses (western wheatgrass), shortgrasses (prairie junegrass) and grasslikes (sedges) = perennial forbs > shrubs. Plant community 1.2 – bluebunch wheatgrass and needleandthread share dominance – the other functional/structural groups will remain the same in descending order.Sub-dominant:
Other:
Additional:
-
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Plant mortality for all functional groups will be low, but there will be some natural mortality of functional groups over time. Prolonged droughts and/or excessive rest may show increases in mortality and decadence for all plant groups. -
Average percent litter cover (%) and depth ( in):
Note: the majority of the litter in the plant community in the Taller Bunchgrass State will be non-persistent. -
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
700 #/acre – 1200 #/acre for the reference community (1.1) with a RV of 950 #/acre.
Production varies based on effective precipitation and natural variability of soil properties for this ecological site.
-
Potential invasive (including noxious) species (native and non-native). List species which BOTH characterize degraded states and have the potential to become a dominant or co-dominant species on the ecological site if their future establishment and growth is not actively controlled by management interventions. Species that become dominant for only one to several years (e.g., short-term response to drought or wildfire) are not invasive plants. Note that unlike other indicators, we are describing what is NOT expected in the reference state for the ecological site:
Cheatgrass, knapweed spp., leafy spurge, sulphur cinquefoil, dalmatian toadflax, Japanese brome, broom snakeweed, fringed sagewort, salsify and dandelion. -
Perennial plant reproductive capability:
All native plants are capable of reproducing sexually and/or vegetatively.
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The Ecosystem Dynamics Interpretive Tool is an information system framework developed by the USDA-ARS Jornada Experimental Range, USDA Natural Resources Conservation Service, and New Mexico State University.
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